A single-atom light switch

Nov 05, 2013

With just a single atom, light can be switched between two fibre optic cables at the Vienna University of Technology. Such a switch enables quantum phenomena to be used for information and communication technology.

Fibre optic cables are turned in to a quantum lab: scientists are trying to build optical switches at the smallest possible scale in order to manipulate light. At the Vienna University of Technology, this can now be done using a single atom. Conventional glass fibre cables, which are used for internet data transfer, can be interconnected by tiny quantum systems.

Light in a Bottle

Professor Arno Rauschenbeutel and his team at the Vienna University of Technology capture light in so-called "bottle resonators". At the surface of these bulgy glass objects, light runs in circles. If such a resonator is brought into the vicinity of a glass fibre which is carrying light, the two systems couple and light can cross over from the glass fibre into the bottle resonator.

"When the circumference of the resonator matches the wavelength of the light, we can make one hundred percent of the light from the glass fibre go into the bottle resonator – and from there it can move on into a second glass fibre", explains Arno Rauschenbeutel.

A Rubidium Atom as a Light Switch

This system, consisting of the incoming fibre, the resonator and the outgoing fibre, is extremely sensitive: "When we take a single Rubidium atom and bring it into contact with the resonator, the behaviour of the system can change dramatically", says Rauschenbeutel. If the light is in resonance with the atom, it is even possible to keep all the light in the original glass fibre, and none of it transfers to the bottle resonator and the outgoing glass fibre. The atom thus acts as a switch which redirects light one or the other fibre.

In the next step, the scientists plan to make use of the fact that the Rubidium atom can occupy different quantum states, only one of which interacts with the resonator. If the atom occupies the non-interacting quantum state, the light behaves as if the atom was not there. Thus, depending on the quantum state of the atom, light is sent into either of the two glass fibres. This opens up the possibility to exploit some of the most remarkable properties of quantum mechanics: "In quantum physics, objects can occupy different states at the same time", says Arno Rauschenbeutel. The atom can be prepared in such a way that it occupies both switch states at once. As a consequence, the states "light" and "no light" are simultaneously present in each of the two glass fibre cables.

For the classical light switch at home, this would be plain impossible, but for a "quantum light switch", occupying both states at once is not a problem. "It will be exciting to test, whether such superpositions are also possible with stronger light pulses. Somewhere we are bound to encounter a crossover between quantum physics and classical physics", says Rauschenbeutel.

This light switch is a very powerful new tool for quantum information and quantum communication. "We are planning to deterministically create quantum entanglement between light and matter", says Arno Rauschenbeutel. "For that, we will no longer need any exotic machinery which is only found in laboratories. Instead, we can now do it with conventional glass fibre cables which are available everywhere."

Related Stories

Researchers at the Vienna University of Technology quantum mechanically couple atoms to glass fiber cables. Now, they have shown that their technique enables storage of quantum information over a sufficiently ...

A light wave oscillates perpendicular to its propagation direction – that is what students learn in school. However, scientists of the Vienna University of Technology (TU Vienna) now perform atom-physics ...

(PhysOrg.com) -- Glass fiber cables are indispensable for the internet  now they can also be used as a quantum physics lab. The Vienna University of Technology is the only research facility in the world, ...

Scientists from the FOM Foundation, the University of Twente and at the Institute for Nanoscience and Cryogenics in France have shown that light sources which usually emit light randomly can be coaxed to ...

Researchers from the Cambridge Research Laboratory of Toshiba Research Europe Limited and the Cavendish Laboratory of the University of Cambridge will today present the world's most secure chat and video conferencing network ...

Recommended for you

(Phys.org)—Physicists have theoretically shown that it is possible to transmit information from one location to another without transmitting energy. Instead of using real photons, which always carry energy, ...

(Phys.org)—For the first time, physicists have performed machine learning on a photonic quantum computer, demonstrating that quantum computers may be able to exponentially speed up the rate at which certain ...

Physicists at the Universities of Bonn and Cambridge have succeeded in linking two completely different quantum systems to one another. In doing so, they have taken an important step forward on the way to a quantum computer. ...

The construction of model quantum systems or simulators that can reveal hidden insights into other, less accessible quantum states requires paying attention to interactions normally overlooked by most theories, ...

In a recent study published in Physical Review Letters, the research group led by ICREA Prof at ICFO Morgan Mitchell has detected, for the first time, entanglement among individual photon pairs in a beam ...

The fact that the neutron is slightly more massive than the proton is the reason why atomic nuclei have exactly those properties that make our world and ultimately our existence possible. Eighty years after ...

User comments : 0

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.